- Alternative Character Interpretation:
- Amberley can be seen as enjoying Cain for his abilities and occasional company, but some lines make her look like a Clingy Jealous Girl, notably when she mentions she'd have found out if Cain was really trying to seduce women he met.
- Similarly, it is possible to interpret Cain's monogamy after getting involved with Amberley as simply his self-defense instincts kicking in: "When dating an Inquisitor, it ain't over till she says it's over!" (His comment about only having room in his life for one lethally dangerous woman comes to mind.)
- Cain is a Dirty Coward, a Lovable Coward, The So-Called Coward, or went through those steps along the way towards his retirement.
- Badass Decay: Averted:
- The Cain novels are more or less the only Warhammer 40K media that convincingly continue to portray Necrons as horrific monstrosities to be feared. Cain has only pulled off one win out of three encounters with the Necrons (and only by blowing them up from orbit), as opposed to his constant success against just about everything else. They are also the one threat thus far that he has adamantly refused to stand and confront, reputation be damned.
- The novels are also some of the few 40K works that manage to juggle presenting all of the main factions as badasses. The one exception is the Eldar, which haven't been featured except for Cain's mentions of his time as a prisoner of the Dark Eldar, which he still has a bit of PTSD over. The Craftworld Eldar finally show up in Chose Your Enemies, where they are indeed deadly opponents.
- The Orks are a more... interesting case. While they are more often than not the "Original Antagonists" that Cain is sent in to fight only to later stumble upon the real threat (Necrons or Tyranids), they are considered the comic relief army in 40K, and the 597th are considered experts at fighting Orks, so it gets played with a little. They get their Day in the Limelight in Death or Glory. In the beginning of that book he mentions that Orks are considered a bit if a joke in-universe... but then he notices the veterans are taking the threat very seriously indeed.
- Darkness-Induced Audience Apathy: Skillfully averted. War Is Hell, but Sandy Mitchell humanizes it so that you actually care (see for example the sequence in Death or Glory where Cain enters a town orks have passed through), and the humor in the series offsets the grimdark nicely.
- Discredited Meme: For many fans, typing HERO OF THE IMPERIUM after every instance of Cain's name.
- "Funny Aneurysm" Moment: If you read in continuity order; a Call-Forward in publication order. In Death or Glory, Jurgen is mostly uninjured by a blow to the head, and Cain says, "It would probably take a bolter shell to crack that thick skull of his." In For the Emperor, Jurgen's skull is fractured near-fatally by... a bolter shell that glances off his helmet.
- Genius Bonus: Overlaps a lot with the Shout Outs on the main page.
- Hilarious in Hindsight:
- In the novel "Caves of Ice," Cain makes reference to a myth going around that at the dawn of the forty-second millenium, the Emperor would get up off his throne and resume command of the Imperium. This was released in 2004. 13 years later, Eighth Edition has just been released and while the Emperor did not get off the Throne, His son, Roboute Guilliman, has.
- "Commissar Donal sends his regards."
- Iron Woobie: Issues of self-esteem are the least of humanity's worries in the Warhammer 40K universe and so it's never emphasized in the books, but Cain has enough trust issues and paranoia to disturb Harry Dresden, and a self-esteem so low that it should be measured in the negative. He goes through his entire life convinced that no one could or should care for him personally, unable to connect with people on any meaningful level, unable to ever credit that he's a remotely decent person or so much as pat himself on the back for the billions of lives he saves, and terrified to trust anyone with his thoughts, lest he be shot for cowardice and deceit. The closest this ever gets to a Lampshade Hanging is when, at their second meeting, Amberley gently implies that she isn't fooled by his facade and suggests that he could try being himself. He practically shits his pants thinking that she's a psyker and is going to have him killed, and he never actually takes her into his confidence even after a century of romance. That's sad.
- Memetic Mutation: One of the few memes originating from TV Tropes: it has become tradition to write HERO OF THE IMPERIUM after Cain's name whenever he appears on another page.
- Squick: The Mechanicus genestealer-breeding experiments in The Greater Good (where convicts are implied to have been forcibly impregnated by infected test subjects) are squicky enough to visibly disturb a visiting Tau.
- Take That, Scrappy!: In The Last Ditch the Tyranids deploy a number of Pyrovores, a notoriously badly designed unit which more likely to blow up itself (and a huge chunk of its allies) than anything useful. Cain exploits this fact by killing them when they're near the Hive Tyrant, and they end up winning the deciding battle of the war for the Imperium.
- They Wasted a Perfectly Good Plot: Fairly early in "The Greater Good", Tau ambassador El'hassai suggests an exchange of observers between the allied Imperial and Tau forces and suggests Cain to be the human representative in the Tau fleet. Instead of agreeing and the book being about Cain fighting alongside the Tau, he nominates ambassador Donali to go instead and sticks with the Imperial force for the rest of the book. As a result, the scene on the cover of Cai back-to-back with a Fire Warrior facing down a swarm of Tyranids never happens and the Tau go on to play almost no part in the rest of the story.
YMMV / Ciaphas Cain